FUNTASTIC FACT: possibly the most minor engine-related nitpick that I have is that in FE8, when you hit R to open a unit's profile, you can't immediately do anything (e.g. open the Help bubble, move from personal data to items, etc) for several frames. This pause doesn't exist in FE7 or 6.
For actual gameplay, though, FE8 is better. Split promos and an actual world map that everyone is too afraid of touching!